Blower assemblies are a common component of vehicle HVAC systems and are designed for maximum efficiency/airflow when operated in commonly known re-circulating and fresh modes. In heater mode within the fresh mode, however, the airflow volume can hinder optimal heating performance within the vehicle by over cooling the engine. As a result, the amount of heated coolant available may not be enough to warm-up the passenger compartment to a desired temperature. Even more, the noise level within the passenger compartment in this mode can reach unsatisfying levels due to the large volume of air moving through typically smaller heat passages and outlets. Accordingly, a need exists for a blower assembly that is tunable or adjustable such that a desired airflow volume can be delivered for all modes of operation including the re-circulating and heater mode combination.
While various solutions to this problem exist, each such solution has its own drawbacks. For example, reducing or restricting the airflow volume in heater mode may be accomplished by reducing the speed of the motor/impeller creating the airflow. In this instance, however, adding such restrictions to control heater airflow volume tends to increase turbulence and noise, vibration, and harshness which are equally untenable.
Alternatively, a maximum voltage applied to the motor/impeller may be clipped or limited thus reducing the maximum airflow volume. While the maximum airflow volume may be appropriately reduced using this approach, a minimum voltage applied to the motor/impeller still results in an airflow volume that is greater than what the occupant wants/needs. The minimum voltage is linked to minimum rotations per minute of the motor, and results in an excessive supply of the heated air available to warm-up the passenger compartment to the desired temperature. Even more, the steps between desired settings of high speed and low speed become compressed to the point that an occupant of the vehicle may be unable to discern any difference between the selected settings.
Another method of tuning the blower assembly such that the desired airflow volume can be delivered for all modes of operation is to adjust the scroll cut-off of the blower assembly. One manner of adjusting the scroll cut-off of a blower assembly is described in U.S. Pat. No. 1,056,813 to McLean. McLean desired to use a volume blower with a large volume between a scroll wall of a blower housing and a wheel (or impeller) as a pressure blower in some instances by controlling the point of cut-off or minimum distance between the blower housing/scroll wall and periphery of the wheel. In McLean's blower assembly, a scroll cut-off is hingedly connected to the scroll wall of the blower housing allowing the scroll cut-off to pivot about a point of attachment. A horizontal portion of the scroll cut-off overlapped an airflow outlet or discharge duct of the blower assembly, and the horizontal portion generally traversed the airflow outlet. A governor was used to adjust the minimum distance between the blower housing/scroll wall and periphery of the wheel dependent upon the speed of the motor.
Another inventor determined a different way of adjusting the scroll cut-off of a blower assembly. Japanese Patent No. 2003042097A describes an adjustment to a distance or air gap between a blower housing/scroll wall and a periphery of a wheel in blower assemblies used in vehicles. The invention is designed to overcome issues involving low frequency noise created when air blown from a centrifugal fan flows backwards into the fan due to high pressure in an air conditioning duct in a foot or a defrost mode of operation. In the blower assembly, a movable nose or scroll cut-off is provided that is pulled by a cable attached to mode selection levers. The scroll cut-off translates along a scroll wall of a housing of the blower assembly. In other modes, the cable pushes the nose or scroll cut-off back along the scroll wall toward the fan to decrease the air gap in the remaining modes of operation. The patent further teaches use of linkages in place of the cable that are actuated to move the scroll cut-off dependent upon a pressure sensor positioned to sense pressure at an airflow outlet. Another discussed alternative, is to attach the scroll cut-off to the scroll wall allowing the scroll cut-off to pivot outward when pulled by the cable thereby altering the size of the air gap. This approach is similar to the McLean approach.
This document relates to a blower assembly having a scroll cut-off that is adjustable using an actuator so that a desired airflow volume can be delivered for all modes of operation in the vehicle. Advantageously, this allows for the vehicle operator to utilize the blower assembly even in the re-circulating and heater modes. Heretofore, the rate of airflow in these modes was too high resulting in an inability to warm-up the passenger compartment to a desired temperature. Even more, the present design avoids the need for cables and/or linkages between the blower assembly and dash mounted controls, and does not result in increased turbulence and noise, vibration, and harshness.